[1] Univ Tennessee, Grad Sch Med, Dept Radiol, Med Ctr, Knoxville, TN 37920 USA
[2] McGill Univ, Res Ctr Studies Aging, Montreal, PQ, Canada
[3] McMaster Univ, Dept Med, Hamilton, ON, Canada
[4] McMaster Univ, Dept Radiol, Hamilton, ON, Canada
[5] Univ Texas Southwestern Med Ctr Dallas, Harold Simmons Comprehens Canc Ctr, Dept Radiol, Div Nucl Med, Dallas, TX 75390 USA